Reliable reporting in wireless mesh network

Abstract

In a wireless mesh network, a battery operated node can select a parent node via which messages are routed to further nodes. The parent node can initially be selected based on signal strength. The node receives acknowledgements for messages sent, if they arrive. The node calculates a reliability indicator of the parent node based on the number of messages for which an acknowledgement has been received. If the reliability indicator exceeds a predetermined threshold the node selects a new parent node, based on second selection criteria. For example, the node with the next greatest signal strength.

The invention claimed is: 
     
       1. A method of controlling a node in a wireless mesh network, the method comprising:
 selecting, based on a first selection criteria, a parent node through which it will communicate with one or more further nodes in the wireless mesh network, wherein the first selection criteria comprises greatest signal strength, 
 sending one or more messages destined to at least one of the one or more further nodes in the wireless mesh network via the selected parent node, 
 calculating a reliability indicator of the parent node by receiving from the parent node acknowledgements received from the one or more further nodes said messages were destined for, 
 selecting a new parent node, based on a second selection criteria, when the reliability indicator exceeds a predetermined threshold, wherein the second selection criteria comprises next greatest signal strength, wherein the step of selecting a new parent node is conditional based on one or more of: the time passed since the last selection of a new parent node, the number of times a new parent node has been selected in a predetermined time period, and the number of nodes capable of operating as a parent node from which a new parent node can be selected, 
 selecting, based on the reliability indicator, a retransmission strategy for retransmitting a message for which no acknowledgement has been received, and 
 executing the retransmission strategy when a message is not acknowledged by the further node said message was destined for. 
 
     
     
       2. The method according to  claim 1 , wherein preference is given to selecting as the new parent node a node other than the current parent node. 
     
     
       3. The method according to  claim 1 , wherein the node is a sensor node sending messages destined for a further node operating as a collector node. 
     
     
       4. The method according to  claim 1 , wherein the retransmission strategy comprises resending messages of a first type and not resending messages of a second type. 
     
     
       5. The method according to  claim 4 , wherein messages of the first type are messages triggered by a single event and/or a periodic update and/or wherein messages of the second type are messages triggered by a burst event. 
     
     
       6. The method according to  claim 1 , wherein the retransmission strategy comprises resending a message as a unicast message via the parent node when no acknowledgement is received. 
     
     
       7. The method according to  claim 1 , wherein the message is resent as a broadcast message via the parent node when no acknowledgement is received. 
     
     
       8. The method according to  claim 1 , wherein the message is resent as a unicast or broadcast message through a further node, not being the parent node, and/or directly from the node, when no acknowledgement is received. 
     
     
       9. The method according to  claim 1 , wherein a message is resent no more than a predetermined maximum number of times. 
     
     
       10. A device arranged for operating as a node in a wireless mesh network, the device comprising:
 an interface arranged for communicating with the wireless mesh network, 
 a processor arranged for sending and receiving messages via the interface, wherein the processor is further arranged for: 
 selecting, based on a first selection criteria, a parent node through which the device will communicate with one or more further nodes in the wireless mesh network, wherein the first selection criteria comprises greatest signal strength, 
 sending one or more messages destined to at least one of the one or more further nodes in the wireless mesh network via the selected parent node, 
 calculating a reliability indicator of the parent node by receiving from the parent node acknowledgements for which an acknowledgement has been received from the one or more further nodes said messages were destined for, 
 selecting a new parent node, based on a second selection criteria, when the reliability indicator exceeds a predetermined threshold, wherein the second selection criteria comprises next greatest signal strength, wherein the selecting the new parent node is further conditional based on one or more of: the time passed since the last selection of a new parent node, the number of times a new parent node has been selected in a predetermined time period, and the number of nodes capable of operating as a parent node from which a new parent node can be selected, and 
 selecting, based on the reliability indicator, a retransmission strategy for retransmitting a message for which no acknowledgement has been received, and wherein the processor is arranged for executing the selected retransmission strategy when a message is not acknowledged by the further node said message was destined to.